<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        h1 {
            text-align: center;
            color: red;
        }

        #root {
            font-size: 60vh;
            text-align: center;
        }
    </style>

</head>
<body>
<h1>倒计时</h1>
<div id="root">

</div>
<script>
    let time = 60
    let a = setInterval(() => {
        time--
        root.innerText = time
        if (time === 0)
            clearInterval(a)
    }, 1000)
</script>

</body>
</html>